Facebook Connect (PHP-Api) doesnt set cookie anymore on certain computers

I have a very strange issue with facebook-connect within my PHP-Webapplication. From one day to the other facebook-connect doesnt work anymore, but only on one on the computers.

This is my code that fails:

// try to get Cookie
$cookie = null;
try {
  $cookie = $_COOKIE['fbs_' . $app_id];
} catch (ErrorException $ex) {
  echo $ex->getMessage();
}

This is the error message i get:

'Undefined index: fbs_myAppId'

I 开发者_如何学运维know that it means, that facebook hasnt set the cookie, like it was supposed to! But the weired thing is, that it works properly on other computers. On the computer where it didnt work, i tried Opera, Chrome, Firefox and IE. I made sure that 3rd Party-Cookies are enabled. And I can properly log on into the normal facebook-website.

So what am I missing???

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The proble was the time-setting on the computer: the time was set one month in advance. Apparently the facebook-cookies have an expire-time of one day. So it was immediatly deleted by the browser.